The Arabic term is not documented in Lisān, Freytag, Lane, Dozy and Wehr.

< Arabic al-fardār. The etymology of the Arabic word is uncertain; it probably derives from a Middle Persian transliteration of the Greek περίοδος. Yamamoto/Burnett 2000, vol. I, 592. The Latin terms are not documented in MLW, DMLBS and LLNMA.